Rheumatoid factor (RF), anti-citrullinated protein antibodies (ACPAs), and C-reactive protein (CRP) are key indicators in diagnosing arthritis. Elevated levels of RF and ACPAs are associated with rheumatoid arthritis, while CRP levels help assess inflammation in the body. Testing these markers provides a comprehensive evaluation of joint health and aids in the early detection and management of arthritis, ensuring timely intervention and better outcomes for patients.